Ghostly electrons: particles flit through atom-thin islands.Confine electrons within microscopically thin layers of material and weird things happen. Experiments on semiconductors in the 1980s demonstrated that to physicists (SN: 10/17/98, p. 247).
Now, two independent research teams have found that electrons imprisoned im·pris·on
tr.v. im·pris·oned, im·pris·on·ing, im·pris·ons
To put in or as if in prison; confine.
[Middle English emprisonen, from Old French emprisoner : en- within a carbon sheet one atom thick behave in yet other odd ways, unlike anything seen in other materials. The electrons act as if they have no mass, so they zip along much faster than electrons moving through semiconductor layers do.
To properly account for the particles' behavior, scientists use equations that include aspects of Einstein's theory of relativity theory of relativity
Einstein’s contribution to the space-time relationship. [Science: NCE, 843–844]
See : Turning Point . The electrons act like a kind of particle known as a Dirac fermion In particle physics, a Dirac fermion is a fermion which is not its own anti-particle. It is named for Paul Dirac. All fermions in the Standard Model, except possibly neutrinos, are Dirac fermions. They can be modelled with the Dirac equation. , which shows up in particle accelerators and cosmic rays cosmic rays, charged particles moving at nearly the speed of light reaching the earth from outer space. Primary cosmic rays consist mostly of protons (nuclei of hydrogen atoms), some alpha particles (helium nuclei), and lesser amounts of nuclei of carbon, nitrogen, . Scientists expect it to also appear in some high-temperature superconductors, gases adjacent to neutron stars, and other exotic circumstances. The new electronic entity looks promising as a benchtop model for investigating the physics of such particles, the researchers say.
A practical payoff is possible as well. The fast electrons could enable the novel carbon sheets to serve as a new type of circuit element in electronic devices capable of operating at frequencies 1,000 times as high as today's components commonly do, says Andre K. Geim of the University of Manchester The University of Manchester is a university located in Manchester, England. With over 40,000 students studying 500 academic programmes, more than 10,000 staff and an annual income of nearly £600 million it is the largest single-site University in the United Kingdom and receives in England, who leads one of the research teams.
For decades, scientists interested in two-dimensional arrangements of electrons have built stacks of semiconductor materials--the sorts of structures ubiquitous in today's microcircuits--to confine the particles to the zone where two layers of a stack meet (SN: 12/18&25/04, p. 394). In some past studies, scientists found unexpected quantum mechanical variations in electrical resistance Electrical resistance
Opposition of a circuit to the flow of electric current. Ohm's law states that the current I flowing in a circuit is proportional to the applied potential difference V. that became known as the quantum Hall effect The quantum Hall effect is a quantum-mechanical version of the Hall effect, observed in two-dimensional electron systems subjected to low temperatures and strong magnetic fields, in which the Hall conductance (SN: 2/22/03, p. 124). Those discoveries eventually garnered Nobel prizes.
Last year, Geim and his team reported that they could remove intact, one-atom-thick flakes of carbon from pieces of graphite (SN: 10/22/04, p. 259). Now, that team and another led by Philip Kim of Columbia University have zeroed in on the electrons in such carbon flakes, which are known as graphene.
In both experiments, the teams coated wafers of silicon with thin layers of silicon dioxide--an electrical insulator. They placed graphene flakes on top of the insulator and connected electrodes to them. Next, the scientists measured the electrical resistance of the flakes to reveal their electronic properties. They found a variation of the quantum Hall effect that had been predicted to occur only when relativistic rel·a·tiv·is·tic
1. Of or relating to relativism.
a. Of, relating to, or resulting from speeds approaching the speed of light: relativistic increase in mass. effects are important.
In graphene, theoretical arguments indicate, electrons interacting as quantum waves effectively cancel each other's masses. As a result, the particles move much faster than ordinary, mass-laden electrons in semiconductors do, Geim says. The groups describe their findings in back-to-back reports in the Nov. 10 Nature.
The "real tour de force" of these new experiments, comments Charles L. Kane of the University of Pennsylvania (body, education) University of Pennsylvania - The home of ENIAC and Machiavelli.
Address: Philadelphia, PA, USA. in Philadelphia, is that "they're able to actually isolate the graphene and to show that indeed it has this [exotic electron] behavior."